The English language term “split-pin” is also known to the German person schooled in the art. This is understood to be a crankshaft for a multi-cylinder combustion engine whose cylinders may be arranged e.g. in V formation, so that the crankshaft is provided with journals offset at an angle and adjoining each other.
Deep rolling tools for the deep rolling of the outer radii or fillets of crankshafts of the above-mentioned type are known e.g. from U.S. Pat. No. 5,575,167 or from EP Patent 0 661 137 B1.
The known deep rolling tools have two housings independent of each other in which deep rolling rollers are rotatably mounted and are pressed by the rolling force respectively into one of the two outer radii or fillets of a split-pin journal. At the same time the crankshaft rotates around its axis of rotation and the housings follow the different movements of the split-pin journals independently of each other. At the same time the housings bear with their flat inner walls upon each other with a supporting element installed between the flat inner walls of the housings. The support is necessary because the reaction forces transmitted by the rolling force from the deep rolling rollers to the housings of the deep rolling roller head must be absorbed. In the case of the first-named US patent the supporting element consists of a pair of ring-shaped flat bearing plates made of teflon, nylon or some other suitable plastic material with good sliding characteristics and low tendency to wear. In the case of the EP patent the supporting element consists of a ring-shaped thrust-bearing unit with cage, installed between the tool housings. The ring-shaped thrust-bearing unit maintains the alignment of the tool housings in parallel vertical planes while the latter are rotated relative to each other around the axis of a motor crankshaft or while the motor crankshaft rotates under the tool housings. It is therefore very important for the thrust-bearing unit to absorb and eliminate the resulting lateral pressure forces produced during the rolling process by the deep rolling rollers opposite of each other and inclined to the outside.
Since the deep rolling rollers are however “shackled” in the axial direction of the crankshaft by the crank arms delimiting the radii or fillets, reactions occur in the upper area of the housing of the deep rolling roller heads, i.e. the area away from the crankshaft. This area has the tendency to gape apart under the deep rolling force. The gaping apart renders the deep rollers uncontrollable and leads to unsatisfactory results.
For this reason measures have already been taken to provide clamping arrangements on the deep rolling devices of which the deep rolling roller heads are a part, their purpose being to suppress the gaping apart of the housings of the deep rolling roller heads. The EP patent describes such a solution (see EP 0 661 137, p. 1, col. 2, lines 4-15, col. 8, lines 18-21 and FIG. 4C).
The means known so far for the suppression of the gaping apart phenomenon are however too far away from the location of that occurrence because of design constraints, so that they cannot be an effective remedy. Due to the natural elasticity of the deep rolling devices in the axial direction of the crankshaft, narrow limitations are imposed on reinforcement by means of clamps.